There is a lot of subjectivity, but your specific definition of Hard Science Fiction would kick out some of the best stories in the Hard Science Fiction canon. Gregory Benford's Timescape is one example.

Remember, I'm not criticizing the stories... just because a story isn't Hard SF, doesn't mean it is less of a good story. Anyway, if my definition differs from everyone else's, that's really of consequence to no one but me.

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Originally Posted by bill_mchale

Further, FTL is not just fringe science these days; modern cosmology believes that most of the Universe is expanding away from us faster than the speed of light .

True, but the "speed limit" of light, while varying depending on the region in the universe, is still considered inviolable by moving objects within that region. In other words, wherever you are, the limit is the limit, and you won't pass it. (I really need Stephen Hawking now!)

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Originally Posted by bill_mchale

Steve, I think the difference between your point of view and mine is that you seem to want experimentally verified results, where I am willing to allow non-mainstream solutions to mainstream theories as a basis for an SF story.

I don't demand "verified results." But I consider some things to have limits which we, as humans, are simply not likely to reach... such as the amount of energy that would be required to push anything more than a few atoms past the speed of light, or through a wormhole to exit at another point in time, which has been suggested by many physicists to be the equivalent of multiple suns' energy output, at best.

If, by "non-mainstream solutions to mainstream theories," you are talking about circumventing a physical law... say, using a tesseract to jump from point to point without traversing physical space... I'm willing to entertain such ideas. But only to the extent that there is some reasonable expectation that such a possibility even exists, and that it is conceivable that it could be deliberately utilized.

It's the difference between knowing about the existence of a black hole, and standing on one.

True, but the "speed limit" of light, while varying depending on the region in the universe, is still considered inviolable by moving objects within that region. In other words, wherever you are, the limit is the limit, and you won't pass it. (I really need Stephen Hawking now!)

The speed of light is constant in a vacuum regardless of where you are. If you find a region of space where the speed of light is different in a vacuum then you have probably just disproved special relativity (and by extension, general relativity as well) .

The basic issue is that space itself is expanding. Relativity limits the speeds that objects with positive rest mass can accelerate to. It does not limit the rate that objects can move apart nor the rate they can approach each other.

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I don't demand "verified results." But I consider some things to have limits which we, as humans, are simply not likely to reach... such as the amount of energy that would be required to push anything more than a few atoms past the speed of light, or through a wormhole to exit at another point in time, which has been suggested by many physicists to be the equivalent of multiple suns' energy output, at best.

Well since the amount of energy to accelerate a single atom past the speed of light is the same as the amount of energy needed to accelerate a planet past the speed of light (i.e. infinite) I am not really worried about that . FTL that relies on acceleration will almost certainly remain implausible.

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If, by "non-mainstream solutions to mainstream theories," you are talking about circumventing a physical law... say, using a tesseract to jump from point to point without traversing physical space... I'm willing to entertain such ideas. But only to the extent that there is some reasonable expectation that such a possibility even exists, and that it is conceivable that it could be deliberately utilized.

Check out Alcubierre Warps.

Granted, I am not saying that time travel or FTL is likely. But I think the ideas are ingrained enough in real physics to be fair game for Hard SF writers to play around with.

I personally don't consider time travel and traveling to alternate realities Hard SF... and especially when accomplished by ships made out of quartz by Victorians using "Platternite." (Not that the story isn't good, mind you--I haven't read it.) Time travel and alternate realities are wonderful and inventive theories, with obvious attractions, but without any concrete basis... which makes them Soft SF.

Time's Eye includes time travel and pocket universes. So some would not consider it Hard SF. The next book in the series is definitely Hard SF. The last book is more of a hard biscuit covered in mold.

Granted, I am not saying that time travel or FTL is likely. But I think the ideas are ingrained enough in real physics to be fair game for Hard SF writers to play around with.

I've used a variation on the Alcubierre Warp myself (Berserker, Sol). But I wouldn't consider it Hard SF at all.

There are many theories that are ingrained in real physics... however, it is the solutions devised to take advantage of those theories that are often lacking. For example, study of the Alcubierre Warp theory also indicates that it is impossible to create an Alcubierre Warp without already having an Alcubierre Warp... a paradox.

Another example: An object larger than a particle traveling through a wormhole... ingrained in real physics. Surviving intact at the other end... not so much (in fact, specifically forbidden by real physics).

So I tend to draw the Hard SF line where theory runs headlong into the wall of reasonable practicality and shatters like an Fabergé egg... whereas in Soft SF you just assume the egg impossibly survived anyway, for the purpose of moving the story along. Again, there's nothing wrong with that, it is a staple of all kinds of fiction, not just SF... and if the reader is willing to accept that the egg survived, in order to enjoy the story, that's great.

So I tend to draw the Hard SF line where theory runs headlong into the wall of reasonable practicality and shatters like an Fabergé egg... whereas in Soft SF you just assume the egg impossibly survived anyway, for the purpose of moving the story along. Again, there's nothing wrong with that, it is a staple of all kinds of fiction, not just SF... and if the reader is willing to accept that the egg survived, in order to enjoy the story, that's great.

Was flying from Paris to NYC in several hours reasonable practicality 100 years ago??

This definition of hard sf is more like mundane sf with emphasis on hard science maybe, rather than let us be "relevant to larger societal issues" that the mundanists proclaim when they tank in the market, and spells boring with capital B most of of the time.

Restricting hard sf to "reasonable practicality" dooms it to irrelevance and a sell by date reached quite soon. Near-future thrillers are at least more exciting, while popular science books are more educative...

To me hard sf is more about a way of writing, a philosophy if you want, that says that there are physical laws in the universe that *are* there and we cannot go around with acts of will, power of love, positive thinking or whatnot, deus-ex-machinas and such, but we may engineer solutions to them.

Was flying from Paris to NYC in several hours reasonable practicality 100 years ago??

We're not talking about relatively minor advances in metallurgy and engine horsepower, gaining us a 4-500% in improvement... we're talking about the difference between a match and a sun, here. How many of Man's technological advances have increased our knowledge and abilities a few trillionfold? See what I'm getting at?

Relevance exists completely independent of Hard or Soft SF... in fact, I'd argue that most of the most "relevant" SF has been soft, not hard, taking advantage of the reality-bending properties of Soft SF to make its point clearer through increased familiarity. Technology only defines a story's possibility... not its value.

True, but the "speed limit" of light, while varying depending on the region in the universe, is still considered inviolable by moving objects within that region. In other words, wherever you are, the limit is the limit, and you won't pass it. (I really need Stephen Hawking now!)

Steve there is no such thing as a "speed limit" based on the speed of light, where nothing can travel faster than the speed of light. There is scientific proof that objects can travel faster than the speed of light.

What you call a speed limit is really more of an asymptote, where objects with mass cannot cross the speed of light, however they can exist below and above the speed.

Any my point was, once you push you 'science' to the point where it is indistinguishable from 'magic', you have walked away from the 'hard sf' corner and into the 'fantasy' corner.

This was why I mentioned Von Neuman's War. The base assumption is that self replicating machines have invaded the solar system. I'm cool with that.

They range in size from nano to macro. I not so cool with that. Macro machines are cool but building them from nano machines raises questions about where the plans are stored and nano machines stop being nano when you ask them to cart around the data to build and program large machines. However, the biggest problem is the energy budget. Where do you get the energy to power/motivate these machines? Entropy asserts that whenever you do something, there is energy lost. The busier your machine is, the more energy is lost.

So, the story requires that I believe that a cloud of nano machines, floating over the landscape, can disassemble a missile, in flight, with no energy release.

Somehow, the writing community got the idea that nano machines will be able to manipulate matter one atom at a time to build any desired molecule or material. Obviously, if you can put it together, you can take it apart. To the best of my knowledge, molecules are generally hard to take apart. Diamond is, perhaps a little extreme. On the other hand, some molecules come apart all to easily (the various fulminates for example).

Anyway, hopefully you get the idea. If the reader has a background that tells him a particular premise isn't going to work, the story cannot, for him, be hard sf.

When I was in high school, I felt good about the range of science that I was learning about through hard sf. Now, many years later, that means I have a huge knowledge base and that means that lots of stories are built on premises that I don't believe will work. I would like to read more hard sf but, what I feel to be, flaws keep getting in the way of the story and so I read lots of outright fantasy instead.

Outright fantasy has whole different set of problems but I'll save them for a more appropriate discussion.

I would like to read more hard sf but, what I feel to be, flaws keep getting in the way of the story and so I read lots of outright fantasy instead.

Outright fantasy has whole different set of problems but I'll save them for a more appropriate discussion.

Today there are 3 writers of hard sf that epitomize its modern incarnation in my opinion: A Reynolds, S. Baxter and G. Egan and they tend to know what they are writing about, though they still write fiction even when making a novel out of General Relativity as Mr. Egan did in Incandescence using a habitat circling a spinning black-hole to allow its inhabitants to discover General Relativity by simple measuring experiments. That novel is available now as e for 6$ from Baen/Night Shade btw and I enjoyed it a lot.

I still believe that the essential difference between fantasy and sf is not the accuracy of science, technology, society... but "philosophy".

SF is mostly "materialistic", philosophically speaking - there are physical laws out there independent of our will - and hard sf focuses a lot on those laws, their consequences and how we engineer our way around, while less hard sf assumes they are there and goes on with the story, but still assumes they are there.

In fantasy, the power of will, love, thoughts, unity with the general magical field however defined affect reality in essential ways. So most fantasy presumes "consciousness" or "will" or "thought" as an intrinsic feature of the Universe/Multiverse, while most sf follows modern science in accepting only matter/energy as intrinsic and consciousness, life and such as emergent artifacts.

Of course there are many wrinkles to this general definition above and lots of exceptions, but generally I think it's essentially accurate.